German Patent Application No. OS 40 03 228 shows a fuel injection valve in which a fuel filter is forced into a fuel inlet connection at a feed end of the fuel injection valve. The fuel filter is provided on its circumference with, for instance, a brass ring which, together with the wall of a fuel inlet connection, forms a pair for the pressing-in of the fuel filter. The pressing of the fuel filter into the fuel inlet connection, however, has disadvantages. For example, in the case of large numbers, there is the danger that the rams do not act uniformly so that a pin-pointed forcing-in press is not possible. With this known type of mounting of the fuel filter there is the disadvantageous possibility of the fuel filter being forced in too far, or the danger of the fuel filter protruding because of insufficient pressing forces.
In particular, the above method has the disadvantage of possibly producing abrasion and chips which can be stripped off upon the pressing as a result of the force fit between the fuel filter and the fuel inlet connection, thereby dirtying the fuel injection valve. Removal of a fuel filter which has been forced into position is practically impossible, since this would entail considerable damage to the fuel injection valve and/or the fuel filter.
In order to hold an O-ring provided at the feed end of the fuel injection valve during the molding around the fuel injection valve, an O-ring holding collar which is separate from the plastic covering is produced as an additional part. The groove formed between the plastic covering, fuel inlet connection, and O-ring holding collar receives the O-ring. The mounting of the O-ring is critical insofar as it must be widened in order to be able to slip over the O-ring-holding collar.
Another disadvantage of the above fuel filter is that, in order to produce the plastic base body of the fuel filter, the sprue must be provided on the so-called clean side upon the injection molding and therefore in the inner region of the fuel filter.
European Patent No. EP 0 348 786 shows a fuel injection valve in which a fuel filter is forced into the fuel inlet connection on the feed end of the fuel injection valve. As a result, all the disadvantages connected with the pressing-in which have been discussed above are present in this valve as well. As the holding collar for the sealing ring, an annular disk is used which is inserted as an additional structural part in a groove on the circumference of the fuel inlet connection. In addition to the undetachable force-fit of the fuel filter, the fuel filter is, for instance, fastened by a flange connection on the fuel inlet connection upstream of the holding collar.
European Patent Application No. EP 0 480 610 describes a fuel injection valve which contains a fuel filter which is forced in place into the fuel inlet connection. Accordingly, all the above-mentioned disadvantages inherent in the forcing in place of the fuel filter can also be present here. As a holding collar, the fuel inlet connection is provided with a curved end so that no additional structural part is required in order to hold the O-ring. A considerable disadvantage results from this in any event since the O-ring must either be widened extremely in order to be able to be pulled over the bent fuel inlet connection, or the shaping of the fuel inlet connection must take place after the mounting, which is particularly disadvantageous.
Fuel filters which are developed together with a shoulder as holding collar for the sealing ring are known from German Patent Application No. OS 39 35 733. The embodiments described therein have the same disadvantages as result from the forcing-in method. The shoulder, which is developed on the fuel filter, serves as a resting surface for the fuel filter on the upstream end of the fuel inlet connection and for the holding of the sealing ring, but it in no way guarantees a dependable attachment of the fuel filter on the fuel injection valve. Therefore, disadvantageous brass-ring members or plastic-ring parts are fastened on the screens which form a part of the pairing of the force-fit with the fuel inlet connection. In this case there is also a great danger of the formation of abrasion and chips which can result in a dirtying which is extremely injurious to the operation of the fuel injection valve. Upon the forcing-in, relatively large pressures must be applied in order to ensure that the shoulder actually rests on the fuel inlet connection. A non-destructive removal of the fuel filter is accordingly impossible. A particular disadvantage of this arrangement is the considerable expense for the manufacture of the fuel filter, the shoulder of which is formed, for instance, by a plurality of disks into which a flange of the screen is inserted. In another embodiment, an additional ring is introduced into the shoulder, which also results in an additional expense.